Shock Wave Overpressure Research Articles

Theoretical calculation for overpressure of air shock wave of explosion induced reaction of reactive material case

In order to study the power of the air shock wave produced by the reactive material driven by explosion, the reaction behavior of the reactive material driven by explosion was analyzed by AUTODYN@ software, and the reaction law of the reactive material was obtained. Considering the chemical energy released by the reactive material, the calculation model of shock wave initial parameters is improved. Combined with dimensional analysis, the theoretical calculation model for overpressure of air shock wave generated by the reactive material driven by explosion is studied. The results show that, under the driving of explosion, the casing made of the reactive material does not react completely. The velocity of air shock wave produced by the charge with reactive material casing is higher than that of the charge with inert material casing. The predicted value of the theoretical calculation model is in good agreement with the experimental results, and the established model can well describe the attenuation law of the air shock wave overpressure generated by the reactive material driven by the explosion.

Study on the shock wave effect and engineering algorithm in the tunnel after structure damage under different explosion conditions

In this paper, according to dimensional analysis, the dimensionless function of the intensity of the air shock wave overpressure of the explosion in structure leaking into a tunnel is established. Forty-eight experiments were carried out focusing on some influencing factors such as explosive charge, explosive depth, ratio of reinforcement, concrete matrix strength, and existence of the structure, revealing the influence laws of explosive charge, explosive height, ratio of reinforcement and concrete matrix strength on the overpressure intensity of air shock wave. Then, engineering calculation methods for leak shock wave effect are obtained, which include the overpressure distribution of shock wave in explosive tunnel in structure, equivalent coefficient of explosive charge compared with explosion in tunnel as well as the reduction factor of shock wave with or without structure.

Wave-Blocking Characteristics of Corrugated Plates under Explosion

Corrugated-board explosion-proof wall is the main means to prevent explosion shock wave damage, and it is important to study the effect of different corrugated plates on the shock wave. Using a high-speed schlieren experimental system and an air overpressure test system, the wave-blocking characteristics of different forms of corrugated plates are comprehensively studied. The schlieren images were used to analyze the influence that the corrugation shape of a corrugated plate has on the shock wave propagation characteristics. The results show that the reflection process of the triangular-, trapezoidal-, and half-cylindrical-shaped corrugated plates exhibit differences. The number of reflected waves from the triangular corrugated plate is much greater than that from the other corrugated plates, and it will consume more energy. The diffraction wave-front velocity has a trend of initially decreasing and then increasing and is also reduced by different degrees by the reflection. Comparative analysis of the schlieren images and the air shock wave overpressure test shows that plates corrugated with different corrugation shapes decrease the diffraction overpressure peak and exhibit a hysteresis.

Airflow disturbance induced by coal mine outburst shock waves: A case study of a gas outburst disaster in China

We explore the magnitude of airflow disturbance in mine roadways induced by gas outburst shock waves. Outburst shock wave propagation in the near-field of the outburst source is established and simulated in three dimensions using FLUENT. The effects in connected but distal roadways are represented by a simplified one-dimensional network model and solved by Flowmaster. A Mesh-based Parallel Code Coupling Interface (MPCCI) is applied to couple the three-dimensional (near source) model and the one-dimensional (distal) model. The coupled model is verified by theoretical analysis and against observations from a coal and gas outburst incident comprising 2887 tonnes of coal that occurred in the Jiulishan coal mine, China and general characteristics of outburst events explored. Simulations demonstrate that airflow disturbance induced by outburst shock waves in the coal mine is principally controlled by the shock wave overpressure and fan pressure provided by the main fan. Of these, the shock wave overpressure exerts the dominant impact. The larger the shock-wave overpressure, the more rapid the decrease of airflow in the roadway branches and the larger the ultimate airflow decrease. Furthermore, the arrival time of the minimum air flow rate is delayed. When the fan pressure is large, the ability to resist airflow disturbance is enhanced and the area subject to countercurrent flow is reduced. The initial air flow rate and the restored air flow rate show less correlation with the shock wave overpressures. However, they are both significantly affected by the pressure of the main fan. This work presents a novel approach for the study of airflow disturbance in underground ventilation networks in coal mines caused by coal and gas outbursts and provides guidance for the design of outburst prevention facilities.

Shock wave evolution and overpressure hazards in partly premixed gas deflagration of DME/LPG blended multi-clean fuel

In order to reveal the shock wave propagation and overpressure hazards of DME (dimethyl ether)/LPG (liquefied petroleum gas) blended fuel in the process of partly premixed gas deflagration, both experimental apparatus and numerical model for multiple-gas explosion and propagation are established. The results show that the overpressure in the sharp-dropping overpressure hazards zone are generally more than 200 kPa, and the distribution range was 5.75–6.75 times of the maximum overpressure hazards zone. The overpressure in the gentle-dropping overpressure hazards zone is the smallest, but its propagation and influence distance is the largest, which can cause certain damage to people and buildings in the far field. The participation of DME at lean-fuel concentration had the greatest effect on the increase of overpressure hazards in the original premixed zone, which could reach 306.6%. The increase of equivalence ratio and the addition of DME fuel both accelerate the superposition of multiple pressure waves. High overpressure risk is always accompanied by high overpressure evolution speed. As equivalence ratio increases, the relationship between the average shock wave velocity and the DME blended ratio was linear, quadratic and cubic, also the flame acceleration mechanism by high burning rate and the flame deceleration mechanism by low combustion heat successively dominates.

Numerical Simulation and Experimental Study on the Anti-explosion Characteristics of Cavity Structure

In order to study the anti-explosion effect of 500*500*200mm (length*width*height) cavity, the corresponding numerical simulation was carried out. It was found that the explosion suppression cavity has a good inhibitory effect on the explosion flame. The simulation results were verified by a field comparison test between the cavity and the straight pipe. It was found that the P1-P2 shock wave peak overpressure suppression rate was -8.11% in the straight pipe, and the F1-F2 flame suppression rate was -25.87%. After the cavity is coupled, the peak overpressure suppression rate of the shock wave becomes 17.12%, and the flame suppression rate becomes 40.85%. Compared with the straight pipe, the shock wave overpressure suppression rate of the cavity is increased by 25.23%, and the flame suppression rate is increased by 66.72%. Through numerical simulation and corresponding experiments, it is found that the cavity of 500*500*200mm (length*width*height) has better suppression effect on gas explosion. And the cavity wave elimination is a structural explosion suppression method, which can effectively suppress the gas explosion and its secondary explosion disaster.

Mitigation Effects of a Water Barrier on Dynamic Loads on the Human Body at Explosions in Tunnels

According to the standards ISO 6184/4 and EN 14373, the efficacy of explosion suppression systems is estimated by maximum reduced (suppressed) shock wave overpressure, recorded in a suppressed explosion event. In addition to this, a significant interest is the capability of explosion protection systems to reduce the dynamic loads on the human body. This task is not considered in standards. The G. Tsulukidze Mining Institute has been studied mitigation of dynamic loads on human by water barrier, generated using the protective system. The system composed of a blast detector, a wireless device for activation and an absorber. During an accidental explosion, the proposed system immediately forms a protective water barrier in the zone to be protected to reduce the overpressure generated by a shock wave. A prototype model has been manufactured, installed and tested under real explosion conditions in the underground experimental base of the G. Tsulukidze Mining Institute. An anthropomorphic test device Hybrid III 50th was used during testing. To register dynamic load generated during an explosion, 7 sensors were installed in different zones of the dummy. Tests were conducted both with the use of the protective system and without it, in conditions when the charge weight was 2 kg, and the distance from the charge to the dummy was 8,5 m. Comparative analysis showed that the protective system, which contains one absorber (may contain several absorbers), reduces the dynamic loads generated in different zones of a human body by 30-50%.

Study on Energy Output Characteristics of Explosives Containing B/Al in the Air Blast

It is a key problem to design and prepare metallized explosives of high energy and low sensitivity. In order to study the effect of the content of the boron/aluminum (B/Al) compound powder on the energy output property of metallized explosives in the air blast, three HMX-based explosives containing B/Al were designed and prepared. Air blast tests of cylindrical samples are performed, accompanied by numerical simulations by the finite element program LS-DYNA. The results show that the shock wave overpressures of explosives containing B/Al are higher than those of explosives containing Al under the same conditions. The deviations between the values calculated by the empirical equation and the measured values are smaller than 3.5 kPa, and the deviations between the values obtained in numerical simulations and the measured values are smaller than 4.9 kPa. Although the Al powder can enter the reaction with detonation products and air easier, the burning time of the boron powder is longer and the released energy is larger. Moreover, as the content of the B/Al compound powder increases, the burning time becomes longer, and the aftereffect work ability and the damage effect become stronger.

Numerical investigation of flame propagation and performance of obstructed pulse detonation engine with variation of hydrogen and air

Pulse detonation engine is a new technique of supersonic wave propagation and stands for high impulsive thrust. The objective of the present investigation is to analyze the detonation wave characteristic of a hydrogen–air mixture in the pulse detonation engine (PDE) having obstacles of blockage ratio 0.5. The three-dimensional reactive Navier–Stokes equations with realizable k − ɛ turbulence model are used to simulate the propagation of combustion flame. The reaction rate of excess hydrogen and excess air is modeled by reduced single-step chemical reaction model and simulated using ANSYS software FLUENT 14.0 code. The simulation results of the shock wave overpressure, deflagration-to-detonation transition run-up distance of different flames and flame velocities are reported at initial boundary condition of 0.1 MPa pressure and 293 K temperature. It has been observed that the obstacles create turbulence in the propagating flame and form strong Mach stems of high temperature, resulting in reduction in accelerated flame run-up length. However, the normalized detonation flame run-up distance increases as the mass of fuel increases in the mixture. Thus, the performance of PDE combustor was observed 4.46% at high overpressure generated by excess fuel (ϕ = 1.3).

Investigation on energy output structure of explosives near-ground explosion

In order to give the energy output structure of typical explosives near-ground explosion in real ground conditions, the free-field shockwave, ground reflection shockwave and Mach wave overpressure time history of composition B explosive, RDX explosive and aluminized explosive were measured by air pressure sensors and ground pressure sensors. The shape of the free-field shock wave, ground reflection shock wave, and Mach wave and explosion flame were captured by high-speed camera. The experimental results show that, at the same horizontal distance from the initiation point, the peak overpressure of explosive shock wave of composition B explosive, both in the air and on the ground, is less than that of RDX and aluminized explosives. At a distance of 3.0 m from the initiation point, the peak overpressure of aluminized explosives is slightly less than that of RDX explosives. Owing to the exothermic effect of aluminum powder, the pressure drop of aluminized explosives is slower than that of RDX explosives. At 5.0 m from the initiation point, the peak overpressure of aluminized explosives is larger than that of RDX explosives. At the same position from the initiation point, among the three kinds of explosives, the impulse of aluminized explosives is the maximum and the impulse of composition B explosives is the minimum. With the increase of the horizontal distance from the initiation point, the height of Mach triple-points (Mach steam) of the three explosives increases gradually. At the same horizontal distance from the initiation point, there is poorly difference in the height of Mach triple-points between aluminized explosive and RDX explosive, and the height of Mach triple-points of composition B explosive is much smaller than that of other two explosives. The maximum diameter and duration of the fireball formed by aluminized explosives are the largest, followed by composition B explosive, and the maximum diameter and duration of the fireball formed by RDX explosive are the smallest.

Experimental study of spontaneous ignition induced by sudden hydrogen release through tubes with different shaped cross-sections

The shock wave dynamics, spontaneous ignition and flame variation during high-pressure hydrogen release through tubes with different cross-section shapes are experimentally studied. Tubes with square, pentagon and circular cross-section shapes are considered in the experiments. The experimental results show that the cross-section shape of the tube has no great difference on the minimum burst pressure for spontaneous ignition in our tests. In the three tubes with length of 300 mm, spontaneous ignition may occur when overpressure of shock wave is 0.9 MPa. When the spontaneous ignition is induced in a non-circular cross-section tube, the possible turbulent flow in the corner of the tube increases can promote the mixing of hydrogen and air, thus producing more amount of the hydrogen/air mixture. As a result, both the peak light signal and flame duration detected in the non-circular cross-section tubes are more intense than those in the circular tube. The smaller angle of the corner leads to a more intensity flame inside tube. When the hydrogen flame propagates to the tube exit from the circular tube, the ball-like flame developed near tube exit is relatively weak. In addition, second flame separation outside the tube is observed for the cases of non-circular cross-section tubes.

Full-scale experimental investigation on the shock-wave characteristics of high-pressure natural gas pipeline physical explosions

In this study, a series of full-scale high-pressure natural gas pipeline physical explosion experiments were performed, in which the overpressure of the shock waves was measured and analyzed. The concept of “physical explosion linear energy (PEXLE)” was proposed and a “PEXLE model” was established to evaluate shock waves in a cylindrical pipeline with high length–diameter ratio. Equations were fitted to describe the characteristics of peak overpressure, positive pressure duration and specific impulse. Results showed that peak overpressure of shock waves is not influenced by the length of pipeline. With the increase of the propagation distance, specific impulse first increases and then decreases. This indicates that the position of the maximum value of overpressure does not correspond with that of the specific impulse.

Numerical estimations of lightning-induced mechanical damage in carbon/epoxy composites using shock wave overpressure and equivalent air blast overpressure

A new approach is proposed for predicting lightning-induced mechanical damage using the shock wave overpressure (SWO) due to lightning arc channel expansion and also its equivalent air blast overpressure (ABO) due to an explosion of chemical potential energy in AS4/3506 carbon/epoxy laminates. The SWOs and equivalent ABOs associated with 124, 247, and 494 kA peak lightning currents were considered. Dynamic responses of the composite laminates due to both the SWOs and ABOs were similar to each other. The spatial variations in the peak compressive and tensile midplane displacements evaluated near the laminate center showed that mechanical damage tended to be symmetric about the laminate midplane. Hashin’s four different damage criteria were implemented to predict fiber/matrix failures. The predicted failure index distributions in the carbon/epoxy plies were nearly identical for both SWOs and ABOs. Except for matrix tension failure predicted at the 494 kA peak current, all damage failure indices increased as the peak current increased, but were smaller than unity, implying no mechanical damage initiation due to lightning strike. These FE results suggest that lightning SWO may not cause significant mechanical damage and it may be possible to interchangeably use either SWO or ABO to predict lightning-induced mechanical damage.

Analysis of Domino Effect Based on Bayesian Probability Explosion and Oil Tank Fire in Mixing Tank Area

Based on the domino effect and Bayesian network, this paper establishes the accident probability model of hybrid storage tank area. Taking a chemical storage tank area as an example to analyze the accident domino effect caused by accident parameters such as thermal radiation and explosion shock wave, we analyzed and calculated the damage probability of shock wave over-pressure and pool fire to adjacent equipment in liquefied gas storage tanks by considered that the occurrence of a pool fire accident in a single tank is a result of the incident. The results show that the control measures are combined with the energy transfer sequence of the accident, so that the safety protection measures proposed under this scenario can more effectively ensure the safety of the chemical tank farm.

Modeling of the whole process of shock wave overpressure of free-field air explosion

The waveform of the explosion shock wave under free-field air explosion is an extremely complex problem. It is generally considered that the waveform consists of overpressure peak, positive pressure zone and negative pressure zone. Most of current practice usually considers only the positive pressure. Many empirical relations are available to predict overpressure peak, the positive pressure action time and pressure decay law. However, there are few models that can predict the whole waveform. The whole process of explosion shock wave overpressure, which was expressed as the product of the three factor functions of peak, attenuation and oscillation, was proposed in the present work. According to the principle of explosion similarity, the scaled parameters were introduced and the empirical formula was absorbed to form a mathematical model of shock wave overpressure. Parametric numerical simulations of free-field air explosions were conducted. By experimental verification of the AUTODYN numerical method and comparing the analytical and simulated curves, the model is proved to be accurate to calculate the shock wave overpressure under free-field air explosion. In addition, through the model the shock wave overpressure at different time and distance can be displayed in three dimensions. The model makes the time needed for theoretical calculation much less than that for numerical simulation.

Experimental Research on Wave Changing of Rapid Assembling Anti-blast Walls

In order to research the ability to weaken the shock wave of the rapid assembling anti-blast walls, the shell explosion test was utilized to compare the shock wave overpressure peak in front of and behind the wall at different scaled distances. The overpressure suppression effect coefficient which reflects the wave dissipating performance of the anti-blast wall was put forward, and the effects of scaled distance, scaled wall height and scaled distance behind the wall on the wave dissipating performance were analysed with the experimental data. The results show that the value of reflected pressure is about 10 times the maximum value of diffraction overpressure, the scaled distance and the measuring distance behind the wall have a great effect on the diffraction overpressure; the diffraction overpressure behind the wall is significantly lower than the free field overpressure when there is no wall, and the overpressure suppression effect of the anti-blast wall can up to 50% or more; the scaled distance and the scaled wall height commonly affect the wave dissipating performance of the anti-blast wall. With the increase of the scaled distance behind the wall, the overpressure suppression effect coefficient gradually decreases. The research results can provide reference and basis for determining the safety distance of the target behind the anti-blast wall.

Blast injuries to carotid artery: development of a finite element model and biomechanical analysis

Objective To construct a three-dimensional finite element model to investigate the biomechanical mechanism of carotid blast injuries. Methods Based on the head and neck CT angiography data of a healthy male volunteer, the 3D geometric model was extracted by Mimics software. The 3D solid model was obtained by fitting the geometric model to the non-uniform rational B-splines (NURBS) by Geomagic Studio software. The mesh of blood vessels, blood and soft tissue was divided by HyperMesh software to obtain the three-dimensional finite element model of the carotid artery. The material parameters and boundary conditions were set, and the vessel wall rupture damage threshold was 1 MPa. The dynamic process of carotid injury caused by MK3A2 grenade explosion shock wave at the distance of 60, 70 and 80 cm to the neck was simulated using the LS-DYNA, generating the shock waveform and peak overpressure. The stress cloud map was used to analyze the stress distribution and damage morphology, and the stress curve was used to analyze the mechanical changes. Results The peak values of shock wave overpressure were 0.45, 0.63 and 0.96 MPa at the distance of 80, 70 and 60 cm away from the explosion center, respectively. At 80 cm, the peak stress of vessel wall was 0.43 MPa, and the vessel wall was not ruptured; at 70 cm, the peak stress of anonyma was greater than 1 MPa, which resulted in small rupture; at 60 cm, the peak stress of both anonyma the ascending aorta were greater than 1 MPa, leading to obvious rupture. The root part of the common carotid artery, anonyma and the arch of the aorta were high stress concentration areas, manifested as high-prevalence areas of damage and rupture. Conclusions The finite element model of explosive carotid artery injury is successfully constructed, which can be used to analyze the mechanical response and damage mechanism of carotid blast injuries. The main cause of injury and rupture is that the sudden change of stress in the process of explosion shock reaches or exceeds the threshold of vascular wall injury. Carotid artery rupture will occur when the vessel wall stress peak is greater than 1 MPa at 60 and 70 cm away from the explosion center, providing references for the clinical treatment and injury prevention. Key words: Carotid artery injuries; Shock wave; Finite element analysis; Biomechanics

Experimental investigation on effects of CO2 additions on spontaneous ignition of high-pressure hydrogen during its sudden release into a tube

Hydrogen is expected to be an alternative energy carrier in the future. High-pressure hydrogen storage option is considered as the best choice. However, spontaneous ignition tends to occur if hydrogen is suddenly released from a high-pressure tank into a tube. In order to improve the safety of hydrogen application, an experimental investigation on effects of CO2 additions (5%, 10% and 15% volume concentration) on the spontaneous ignition of high-pressure hydrogen during its sudden expansion inside the tube has been conducted. Pressure transducers are used to record the pressure variation and light sensors are employed to detect the possible spontaneous ignition. It is found that the shock wave overpressure and the mean shock wave speed are almost the same inside the tube for different CO2 additions under the close burst pressures. For cases with more CO2 additions, the ignition detected time is longer and the average speed of the flame, the maximum value of light signals and the detected duration time of spontaneous ignition are smaller. It is shown that minimum burst pressure required for spontaneous ignition increase 1.47 times for 15% CO2 additions. The minimum burst pressure required for spontaneous ignition increases from 4.37 MPa (0% CO2) up to 6.41 MPa (15% CO2). With the increasing of CO2 additions, it requires longer distance and longer time for hydrogen and oxygen to mix and thus longer ignition delay distance/time. The results showed that additions of CO2 to air have a good suppressing effect on hydrogen spontaneous ignition.

Impact of Water Mist Thickness on Shock Wave Attenuation

Explosion protection systems for underground structures are designed to create a suppressing barrier between the site of explosion and the facility to be protected. Studies have shown that water mist, provided that its properties are correctly selected, can effectively reduce shock wave overpressure in tunnels. The influence of droplet sizes and concentration of water in mist on shock wave mitigation processes have been studied by various researchers through experiments and modelling. However, the effect of geometric dimensions of mist on shock wave attenuation in tunnels has not been sufficiently studied.This paper addresses the influence of water mist thickness on blast overpressure under identical mist properties and explosion conditions in the tunnel. The study of such influence is essential for the proper design of the protective system. Experiments were conducted in the tunnel of the underground experimental base of the Mining Institute, Tbilisi, Georgia. The methodology employed envisaged the measurement of overpressures in the tunnel with the mist generated by the spray system. At different stages of experiments, the water mist thickness was 1.6m, 2.6m and 3.8m. Experiments were carried under the following conditions: charge weight - 2 kg; distance from the charge to the mist - 3.5 m, from the charge to the sensors - 11.5 m, droplet size distribution - 10-260μm, Mist density - 1.45 l/s•m3. In the test zone the height of the tunnel was 2.2 m, width - 2.2 m, cross-section - 4.4m2. The results of the experiments showed that the water mist thickness has an influence on the shock wave overpressure. Under the conditions of experiments carried out by us, the increase of the mist thickness by 3.1 times allowed to reduce the overpressure by 34%.

Pressure Load Characteristics of Nonideal Explosives in a Simulation Cabin

In this study, an aluminum‐containing charge was exploded in an enclosed simulation cabin to explore the characteristics of two types of damaging pressure loads formed by internal explosions: the first incident shock wave and the quasistatic pressure. A high‐frequency piezoelectric sensor was used to measure the first incident shock wave and a low‐frequency piezoresistive sensor was used to measure the quasistatic pressure. After obtaining effective experimental data, the experimental results were compared with the values obtained by the classical calculation model. The results show that the pressure loads generated by the internal explosions from the ideal explosive and the aluminum‐containing explosive share similar load characteristics, given the same mass and benchmark explosive. The difference between the two explosives primarily lies in the amplitude of the load parameters. The aluminum‐containing explosive has lower first incident shock wave and higher quasistatic pressure than that of the ideal explosive. For the peak overpressure of the first incident shock wave, the explosion shock wave load parameters of the aluminum‐containing explosive, which are calculated based on the explosion heat theory, are higher than the measured values. The peak quasistatic overpressure is directly related to the total energy released by the explosion; however, they are hardly correlated with the reaction process. Therefore, the aerobic postcombustion reaction of the aluminum‐containing explosive does not affect the analysis and calculation of the peak quasistatic overpressure. As a result, given the heat value of the explosive, the peak quasistatic overpressure of the explosive can accurately be obtained.